Both low density lipoproteins (LDL) and very low density lipoproteins (VLDL) have been implicated as positive risk factors in the genesis of atherosclerosis, whereas high density lipoprotein (HDL) concentration is an independent negative risk factor. Both diabetes and obesity are associated with changes in plasma lipoproteins and these changes may be related to the increased prevalence of cardiovascular disease. We are studying lipoprotein composition in obese and diabetic Pima Indians. Cholesterol and triglycerides are being measured in VLDL, LDL, and HDL, as well as in HDL subclasses isolated by ultracentrifugation. Comparison of data on nondiabetic Pimas to those of Caucasians in the LRC survey indicates Pima males and females have lower total and LDL cholesterol. On the other hand, total and VLDL triglyceride concentrations are higher. Both Pima males and females have lower HDL cholesterol than LRC Caucasians, and there is no sex difference in HDL in the Pimas. Total and LDL cholesterol were not associated with obesity, but total and VLDL triglyceride increased with increasing obesity. There was a strong negative association between obesity and HDL cholesterol. Measurements of total cholesterol and triglyceride and HDL cholesterol were also performed on samples from 2 South Pacific populations - the Polynesians of Rarotonga and the Melanesians of New Hebrides. In both, HDL cholesterol was low, and, as in the Pimas, there were no sex differences in HDL cholesterol. Cholesterol and triglyceride in Raratongans were higher than in the population of New Hebrides, and there appeared to be a relation between the occurrence of hyperlipemia and increased cardiovascular disease (CVD) in Raratonga. The data to date on lipoprotein composition of these various populations suggest there are racial differences in lipoprotein distributions which may be important in the determination of the prevalence of CVD. Our plans are to analyze the data on lipoprotein composition and its relation to diabetes and CVD in the Pimas and to compare our data to Caucasian and other diabetic groups.